The present invention relates to a thrust reverser for a fan-type turbojet engine, more particularly such an engine having a fan housing that is axially shorter than the turbojet engine housing wherein the thrust reverser doors are located on the fan housing.
Fan-type turbojet engines are well known in the art and typically comprise a jet engine housing defining a primary gas flow duct through which pass hot gases emanating from the jet engine and a fan housing generally coaxially arranged around the engine housing and defining therebetween a generally annular secondary gas flow duct through which pass cold gases from the fan. It is also known to incorporate thrust reversers in such engine structures and, particularly wherein the fan-type engine is of the high bypass ratio type, it is known to have the thrust reversers acting solely or primarily on the gases passing through the secondary gas flow duct.
FIG. 1 of the attached drawings illustrates a known thrust reverser design comprising a forward, or upstream, stationary structure 1 which forms an outer boundary of the secondary gas flow duct, a movable portion 2 and a stationary rear, or downstream, annulus 3. The stationary forward structure 1 comprises an outer panel 4, an inner panel 5 having a deflecting edge 8 and which forms the external boundary of the secondary gas flow duct. A front frame 6 interconnects the outer and inner panels 4 and 5, respectively. The frame 6 also supports an actuating system which drives the movable portion 2 between its forward thrust position (illustrated in FIG. 1) and its reverse thrust position (illustrated in FIG. 2). The movable portion 2 typically comprises thrust reverser doors 7, the number of which may vary in relation to each particular application and typically comprises two, three or four such doors 7 which together subtend an annular assembly which cooperates with the stationary portion of the engine.
FIG. 2 is a partial perspective view of a known thrust reverser system used in a bypass-type turbojet engine wherein the thrust reverser comprises four doors 7, two of which are illustrated in FIG. 2 in their open, or reverse, thrust positions. Each door is connected to a control means such as an actuator 7a to move it between its forward thrust position and its reverse thrust position.
Illustrative designs of turbojet engine thrust reversers with pivoting thrust reverser doors can be found in the following U.S. Pat. Nos. 4,894,985; 4,858,430; 4,916,895; 4,914,905; 4,976,466; 4,960,243; and 5,039,171.
Although the known designs of movable door thrust reversers have been generally satisfactory, in certain applications, these known types have encountered substantial difficulties, and under certain conditions, may be impossible to use. In jet engine assemblies with very high bypass ratios and wherein the fan housing is substantially axially shorter than the jet engine housing so as to provide an axially short secondary flow duct corresponding to the separate flow mode of operation, the use of known thrust reverser door systems have proven unsuitable.